Add a "reveal all" or "hide all" layer mask

addMask.jsx

addMask("reveallAll");

function addMask(maskVisibility) {
    // maskVisibility = "revealAll" or "hideAll"
    var c2t = function (s) {
        return app.charIDToTypeID(s);
    };
    var s2t = function (s) {
        return app.stringIDToTypeID(s);
    };
    var descriptor = new ActionDescriptor();
    var reference = new ActionReference();
    descriptor.putClass(s2t("new"), s2t("channel"));
    reference.putEnumerated(s2t("channel"), s2t("channel"), s2t("mask"));
    descriptor.putReference(s2t("at"), reference);
    descriptor.putEnumerated(s2t("using"), c2t("UsrM"), s2t(maskVisibility));
    executeAction(s2t("make"), descriptor, DialogModes.NO);
}